RemoveDefer & typescript

[tech-meppem]

I added an option called 'removeDefer' which removes the defer tag.
This is useful if you set the scriptLoading: 'defer', option on the HtmlWebpackPlugin, as this way, you can have:

new HtmlWebpackPlugin({
    // Defer script loading for faster loading
    scriptLoading: 'defer',
    chunksConfig: {
        async: ["MyAsyncEntry"],
        removeDefer: ["MyAsyncEntry"],
    },
}),

And then MyAsyncEntry will only have async="async" as an attribute, and no longer will have defer="defer" as well.

I also added a typescript d.ts file, which augments the HtmlWebpackPlugin options to provide the types.
Useful if you have your webpack files in typescript (like I do).

[architgarg]

@tech-meppem LGTM, Is there anything else you would like to add to this PR or should I merge this one?